Hi, why dont you import one map from one location to another? Some information will be lost, that would be the same like r.resamp.stats.
http://grass.itc.it/grass64/manuals/html64_user/r.proj.html Achim Patrice Dumas schrieb: > Hello, > > I have 2 locations, one with a lambert projection with a 1 km grid > (comes from hydro1k), covering africa, and the other with a longitude latitude > projection with a 0.5 decimal degrees grid (covering the world). I have a > raster map on the lambert location that has values of 1 for a given area and > 0 (or null) otherwise (corresponds with upstream basins) and I would like to > compute the corresponding area covered on the lonlat grid. This would lead > to a value for each cell in the lonlat grid corresponding with the fraction > of the grid cell covered by 1 in the lambert map. So, for example, if the > cell is completly in the area in the lambert map, the value in the lonlat map > should be 1, and if half of the area of the cell from the lonlat map > is covered by ones in the lambert map, the value in the lonlat map should > be 0.5. > > If the two maps were in the same location, I could set the region > to be the one of the lonlat map, and do > > r.resamp.stats -w input=lambert_map output=fraction_covered > > But r.resamp.stats doesn't work with maps from different locations. > And it seems to me that r.proj forgets the information about the > initial grid although in this case it should be kept. > > I have read the manual pages and the wiki but couldn't find anything > answering my question, except that it seems to be something uneasy to > do in grass, since operations on different locations cannot be done in order > to avoid losses of accuracy: > http://grass.osgeo.org/wiki/Location_and_Mapsets > > I may be wrong, but it seems to me that this kind of use of ratios to > interpolate from a grid to another would be something that is done > regularly, and I guess that other kind of computations requiring > that geographic informations are not lost for each map would also > be useful. > > -- > Pat > _______________________________________________ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user